【作者】 王健健；

【导师】 王艳芹；

【作者基本信息】 华东理工大学 ， 工业催化， 2014， 博士

【摘要】 进入21世纪,经济的飞速发展,全球人口规模的不断增长,引发了全球性的能源危机。同时,由于不可再生化石能源的大量开采、使用,使得环境污染和生态破坏等问题日益突出,因此开发可再生的新能源成为当务之急。生物质是一种来源广泛的可再生绿色能源,采用高效的催化方法可将生物质转变为精细化学品和生物燃料,以满足社会发展的需求。本文针对生物质高效转化的问题,从催化化学和降低生产成本的角度,从以下几个方面开展了探索性的研究工作：1.采用一步水热碳化法制备了一种新型的碳基固体酸催化剂,其具有较高的酸量且表面含有-SO3H,-COOH和-OH三种官能团。将该催化剂应用到果糖脱水制备5-羟甲基糠醛(HMF)的反应中,以二甲基亚砜(DMSO)为溶剂,在温和反应条件下,底物果糖完全转化,产物HMF得率高达91.2%；增加果糖的浓度(从7至20wt.%),HMF得率也可以保持在80%以上。研究发现催化剂表面上的磺酸和羧酸之间存在协同作用,两者共同促进果糖快速且高效地脱水转化为HMF。2.进一步改进上述的碳基固体酸催化剂以增加其比表面积(可达189m2·g-1),并采用THF+DMSO为反应溶剂(7：3,v/v),HMF得率提高到98%。研究表明该催化剂大大降低果糖脱水反应的能垒,反应活化能为50.3kJ·mol-1,而这一活化能要远低于以硫酸或酸性离子交换树脂为催化剂的反应活化能。此外,采用简单的萃取方法,可以将大部分HMF从反应液中分离出来,实现了产物HMF与高沸点溶剂DMSO的有效分离,分离出来的HMF纯度可达96.4%。3.采用离子交换法制备了Sn-Mont固体酸催化剂,其属于中强酸类且表面含有Lewis和Br(?)nsted两种酸性位。以THF+DMSO为溶剂,单一Sn-Mont催化剂即可将葡萄糖完全转化,HMF得率达到53.5%。研究表明催化剂结构中的Sn离子作为Lewis酸中心用于葡萄糖到果糖的异构化反应,而活性Sn-OH作为Br(?)nsted酸中心用于将生成的果糖转化为HMF。值得一提的是,在THF/H2O-NaCl两相反应体系中,该催化剂也可催化淀粉和纤维素高效转化,HMF得率分别达到44.4和39.1%。4.以Sn-Mont为催化剂,在THF/H2O-NaCl两相体系中,混合糖(木糖和葡萄糖)转化完全,糠醛和HMF的得率分别达到50和65%左右。当引入另一种具有相似B/L比例但酸量更高的NbOPO4固体酸作为共催化剂时,糠醛和HMF的得率分别提高到76.8和68.6%,这主要归功于Sn-Mont和NbOPO4催化剂之间的协同作用,Sn-Mont有利于葡萄糖的转化,而NbOPO4用于高效转化木糖。原生生物质也可以在该反应体系高效转化,糠醛和HMF的质量收率均维持在20%左右,且原生生物质中的木质素和无机盐不会对半纤维素和纤维素的转化造成影响。5.采用共沉淀法制备了Ru/Co3O4催化剂,该催化剂在氢解糠醛和HMF的反应中显示出了优异的催化活性,以混合糖或原生生物质的反应液为底物,在温和反应条件下,该催化剂均可将反应液中的糠醛和HMF转化为MF和DMF,两者得率均在90%左右,避免了分离纯化糠醛和HMF的过程。研究表明,催化剂中Ru颗粒主要起到活化氢气的作用,而CoOx活性物种用于吸附中间产物和断裂C-O键,从而将糠醛和HMF氢解为MF和DMF。更多还原

【Abstract】 With rapid development of economy and increase of population size, the global crisis of energy emerges in the twenty-one century. Meanwhile, due to the excessive exploit of non-renewable fossil fuels, the problems of environment pollution and ecological damage have come out, and how to develop new technical route to produce renewable biofuels has become a focus of scientific research. Lignocellulosic biomass has been regarded as renewable green-energy, and efficient production of fine chemicals and biofuels from lignocellulosic biomass would meet with the growing demand of economic development. In this thesis, from the point of catalytic chemistry and reducing the production costs, a series of novel catalysts have been prepared and used to convert lignocellulosic biomass to fine chemicals and liquid biofuels. The main research results are achieved as follows:1. A novel carbon-based solid acid catalyst with high concentration of acid sites, bearing-SO3H,-COOH and-OH groups, has been easily synthesized via one-step hydrothermal carbonization approach. Such carbonaceous catalyst was used in the dehydration of fructose into5-hydroxymethylfurfural (HMF). Fructose can be completely converted in DMSO solvent under mild conditions, and the yield of HMF was up to91.2%. When the concentration of fructose increased from initial7to20wt.%, the yields of HMF maintained around80%. Compared to other acidic catalysts, the multiple functional groups on the carbonaceous catalyst enhanced the adsorption of fructose, but did not inhibit the fast desorption of HMF from the catalyst surface. Meanwhile, the synergic effect between surface carboxylic acid and sulfonic acid groups promoted the efficient conversion of fructose to HMF.2. Fructose can be fully converted in THF/DMSO mixed-solvent (7:3, v/v) catalyzed by a novel carbon-based solid acid catalyst with high surface area (189m2·g-1) under mild conditions, and the yield of HMF was up to98%. From the results of kinetic analysis, the extraordinary activity of carbonaceous catalyst was attributed to its greatly lowering down the energy barrier of the dehydration reaction of fructose, and the activation energy was50.3kJ·mol-1, which was much lower than that catalyzed by sulfuric acid or ion-exchanged acid resin. Especially, with the addition of DEE and H2O into the reaction system to extract HMF from the reaction solution, high purity of HMF (96.4%) can be obtained, realizing the goal of separation of HMF from high boiling point solvent of DMSO.3. A novel Sn-Mont solid acid catalyst, which had moderate to strong acid strength and contained both Lewis and Bronsted acid sites was synthesized easily via an ion-exchanged method. Single Sn-Mont catalyst can be directly used to completely convert glucose to HMF in THF and DMSO mixed solvent under mild conditions, and the yield of HMF was up to53.5%. It was found that Sn ions in the structure of Sn-Mont catalyst was used as the Lewis acid sites to isomerize glucose to fructose and these active Sn-OH groups was used as the Bronsted acid sites to convert the generated fructose to HMF. Especially, the yields of HMF were up to44.4and39.1%from starch and cellulose in THF/H2O-NaCl biphasic system, where THF was used as the extraction agent to promote the generated HMF from aqueous phase transferring to organic phase.4. The mixtures of xylose and glucose can be simultaneously and completely converted catalyzed by single Sn-Mont catalyst in THF/H2O-NaCl biphasic system under mild conditions, and the yields of furfural and HMF were about50and65%, respectively. Besides, the yields of furfural and HMF can be enhanced to76.8and68.6%at the same reaction conditions with addition of another NbOPO4solid acid catalyst with similar ratio of Bronsted to Lewis acid sites and higher acid amounts. Such excellent performances were attributed to the synergistic effect between Sn-Mont and NbOPO4catalyst, where Sn-Mont catalyst was beneficial for conversion of glucose to HMF and NbOPO4catalyst was used to efficiently convert xylose to furfural. This mixed catalysts also have exhibited excellent performances in the conversion of lignocellulosic biomass, and the total mass yields of furfural and HMF were always around20%. Meanwhile, lignin and inorganic salts in lignocellulosic biomass did not affect the conversion of hemicellulose and cellulose into furfural and HMF.5. A Ru/Co3O4catalyst easily prepared via co-precipitation method has showed extraordinary catalytic performances in the simultaneously hydrogenolysis of furfural and HMF. Meanwhile, furfural and HMF in the reaction mixture from dehydration of mixed sugars or lignocellulosic biomass can be directly converted to MF and DMF catalyzed by such Ru/Co3O4catalyst under mild conditions, and the yields of MF and DMF were around90%. This approach not only avoided the complicated separation and purification processes of furfural and HMF from the reaction mixture, but also lowered down the costs of biofuels production, realizing the goal of efficient production of liquid biofuels from renewable lignocellulosic biomass. It was confirmed that the Ru particles in the reduced catalyst were used to activate hydrogen, and active CoOx species have played important roles in the adsorption of intermediates and breakage C-O bonds, resulting in the formation of MF and DMF from furfural and HMF.更多还原